This invention relates to a connection system of the multiplex type, i.e. with communication channels accessible to a plurality of users provided between a master processing unit and groups of slave units connected to one of such channels respectively, with the possibility of controlling the exchange of communication between the channels. In particular the connection system according to this invention can be applied to a plurality of units associated with the electrical devices in a vehicle, and especially for the activation and control of electrical devices associated with a motor vehicle door, such as for example the window winding device, the door locking device, the device actuating the various electrical components of an outside rear-view mirror, and the device with manual control switches for control of the components in the various abovementioned devices as described in Italian application no. 67158-A/89 lodged on the 7 Mar. 1989 entitled: "Activation and control system for a plurality of electrical devices in a vehicle".
As is known, in master-slave communication systems each slave unit may be connected to the master processing unit by its own communication line. This arrangement however results in a high number of input-output ports in the master unit, and a high number of communication lines, as a result of which the complexity of the cabling is a disadvantage in comparison with systems of the multiplex type. Systems have therefore been proposed in which all the slave units are connected to the master unit by a single communication bus. A fault on this line however compromises the functioning of the entire system.